The catamaran was probably the earliest twinhull vessel to appear. The catamaran consisted of a platform member having two hull members suspended from the platform, one on either side of the platform. The hulls are of uniform cross section and their sides were generally parallel planes.
Subsequently, small waterplane twin hull vessels were developed (sometimes referred to as SWATH ships) by the United States Navy. This type of vessel was a modification of the catamaran in which there were two submerged hulls of uniform cross section which were connected to the platform by elongated struts which have a cross section substantially smaller than the cross section of the submerged hull, hence the small waterplane twin hull characterization.
More recently, the Naval Ocean System Center at San Diego and Honolulu developed a design characterized as a "Two-strut" per side ship. These ships were characterized by submerged twin hulls of uniform cross section and the hulls were suspended from the platform by two narrow struts, one making a connection between the forward end of the submerged hull and the platform and the other making the connection between the after end of the submerged hull and the platform.
The design of the ship of the present invention employs the two-strut per side concept, but by the employment of submerged hulls which have varying cross sectional areas along the hull lengths and by employing strut-like connections between the submerged hulls and the platform which flare outwardly both longitudinally and transversely from the waterline to the junction with the platform, achieves improved stability, improved reduction of wave forces and the more effective use of applied horsepower.